After a recent trip to the framer, they presented multiple framing options for floating a piece I own. Their best "conservation/archival" recommendation was to have the front actually touching the plexiglass, in order to keep the piece "flat". They claim it's inert properties and lack of temperature change will make it "safe" and not ruin the art over time. I've been warned that screen prints touching _glass_ can be dangerous, and the art can stick to the glass if temperature change happens.

That's because paper changes shape as the humidity fluctuates. It's really best to separate any glazing from the print. But you can make an informed decision whether it's worth doing spending the money to float it properly. There are a lot of factors to consider: the cost of the print, the type of print, the density of the ink, the type of paper used, etc.